A touch position sensor is a device that can detect the presence and location of a touch by a finger or by another object, such as a stylus. A touch position sensor, for example, can detect the presence and location of a touch within an area of an external interface of the touch position sensor. In a touch sensitive display application, the touch position sensor enables direct interaction with what is displayed on the screen, rather than indirectly with a mouse or touchpad.
There are a number of different types of touch position sensors, such as resistive touch screens, surface acoustic wave touch screens, capacitive touch screens etc. A capacitive touch screen, for example, may include an insulator, coated with a transparent conductor in a particular pattern. When an object, such as a finger or a stylus, touches or is provided in close proximity to the surface of the screen there is a change in capacitance. This change in capacitance may be sent to a controller for processing to determine the position of the touch.
As the technology of touch screens and the resolution available in portable interactive touch position sensors advances, at least some users may prefer to use a stylus. A stylus generally is linearly shaped and has a smaller contact area than a finger which may make it easier to differentiate between touch icons on a screen. In addition, a stylus may have a sensing tip of rounded design in order to avoid damaging the very sensitive surfaces of the screens.
However, a stylus having a rounded tip may have limited contact with the flat screen of a touch position sensor. As a result, the ability of the touch screen to sense the position of a stylus having a single, ball-shaped tip may be limited.